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    <ul class="crumbs"><li><a href="../index.html">Home</a></li><li><a href="../services.html">Services</a></li><li><a href="index.html">kinds</a></li><li><a href="index.html#P">Preliminaries</a></li><li><b>How To Include This Module</b></li></ul></div>
<p class="purpose">What to do to make use of the kinds module in a new command-line tool.</p>

<ul class="toc"><li><a href="P-htitm.html#SP1">&#167;1. Status</a></li><li><a href="P-htitm.html#SP2">&#167;2. Importing the module</a></li><li><a href="P-htitm.html#SP3">&#167;3. Using callbacks</a></li></ul><hr class="tocbar">

<p class="commentary firstcommentary"><a id="SP1" class="paragraph-anchor"></a><b>&#167;1. Status.</b>The kinds module is provided as one of the "services" suite of modules,
which means that it was built with a view to potential incorporation in
multiple tools. It can be found, for example, in <a href="../inform7/index.html" class="internal">inform7</a> and
<a href="../kinds-test/index.html" class="internal">kinds-test</a>.
</p>

<p class="commentary">By convention, the modules considered as "services" have no dependencies on
other modules except for <a href="../foundation/index.html" class="internal">foundation</a> and other "services" modules.
</p>

<p class="commentary">A tool can import <a href="index.html" class="internal">kinds</a> only if it also imports <a href="../foundation/index.html" class="internal">foundation</a>,
<a href="../words-module/index.html" class="internal">words</a>, <a href="../syntax-module/index.html" class="internal">syntax</a>, <a href="../inflections-module/index.html" class="internal">inflections</a> and <a href="../linguistics-module/index.html" class="internal">linguistics</a>.
</p>

<p class="commentary firstcommentary"><a id="SP2" class="paragraph-anchor"></a><b>&#167;2. Importing the module.</b>We'll use the term "parent" to mean the tool which is importing <a href="index.html" class="internal">kinds</a>,
that is, which will include its code and be able to use it. As with any
imported module,
</p>

<ul class="items"><li>&#9679; The contents page of the parent's web must identify and locate the
module:
</li></ul>
<pre class="displayed-code all-displayed-code code-font">
<span class="element-syntax">Import</span><span class="plain-syntax">:</span><span class="string-syntax"> somepath/kinds</span>
</pre>
<ul class="items"><li>&#9679; The parent must call <a href="1-km.html#SP3" class="internal">KindsModule::start</a> just after it starts up, and
<a href="1-km.html#SP3" class="internal">KindsModule::end</a> just before it shuts down. (But just after, and just
before, the corresponding calls to <a href="../foundation/index.html" class="internal">foundation</a>.)
</li></ul>
<p class="commentary firstcommentary"><a id="SP3" class="paragraph-anchor"></a><b>&#167;3. Using callbacks.</b>Shared modules like this one are tweaked in behaviour by defining "callback
functions". This means that the parent might provide a function of its own
which would answer a question put to it by the module, or take some action
on behalf of the module: it's a callback in the sense that the parent is
normally calling the module, but then the module calls the parent back to
ask for data or action.
</p>

<p class="commentary">The parent must indicate which function to use by defining a constant with
a specific name as being equal to that function's name. A fictional example
would be
</p>

<pre class="displayed-code all-displayed-code code-font">
<span class="plain-syntax">    </span><span class="function-syntax">@d</span><span class="plain-syntax"> EXPRESS_SURPRISE_KINDS_CALLBACK Emotions::whoa</span>

<span class="plain-syntax">    =</span>
<span class="plain-syntax">    </span><span class="element-syntax">void Emotions:</span><span class="plain-syntax">:</span><span class="string-syntax">whoa(text_stream *OUT) {</span>
<span class="plain-syntax">        WRITE("Great heavens!\n");</span>
<span class="plain-syntax">    }</span>
</pre>
<p class="commentary">The following alphabetical list has references to fuller explanations:
</p>

<ul class="items"><li>&#9679; <span class="extract"><span class="extract-syntax">DETERMINE_SCALE_FACTOR_KINDS_CALLBACK</span></span>, if provided, is called to give
the "scale factor" for a kind. See <a href="../values-module/3-lp.html" class="internal">Literal Patterns (in values)</a> for the
use of this; here, it appears in <a href="2-uk.html#SP18" class="internal">Kinds::Behaviour::scale_factor</a>.
</li><li>&#9679; <span class="extract"><span class="extract-syntax">HIERARCHY_GET_SUPER_KINDS_CALLBACK</span></span> is called to ask what the superkind
of a kind is. See <a href="2-tlok.html#SP6" class="internal">Latticework::super</a>.
</li><li>&#9679; <span class="extract"><span class="extract-syntax">HIERARCHY_ALLOWS_SOMETIMES_MATCH_KINDS_CALLBACK</span></span> is called to ask if q
kind can contain sometimes-matching subkind instances. See
<a href="2-tlok.html#SP13" class="internal">Latticework::order_relation</a>.
</li><li>&#9679; <span class="extract"><span class="extract-syntax">HIERARCHY_MOVE_KINDS_CALLBACK</span></span> is called to ask us to put make one
kind a subkind of another. See <a href="2-knd.html#SP24" class="internal">Kinds::make_subkind</a> and
<a href="2-knd.html#SP23" class="internal">Kinds::new_base</a> &mdash; there are two ways this can happen.
</li><li>&#9679; <span class="extract"><span class="extract-syntax">HIERARCHY_VETO_MOVE_KINDS_CALLBACK</span></span> is called to give the parent tool a
chance to veto any proposed subkind. (Inform uses this, for example, to catch
the case of somebody making "region" a subkind of some other kind of object.)
See <a href="2-knd.html#SP24" class="internal">Kinds::make_subkind</a>.
</li><li>&#9679; <span class="extract"><span class="extract-syntax">NEW_BASE_KINDS_CALLBACK</span></span> is called when a new base kind (properly
speaking, a new arity-0 kind constructor) is made. See <a href="2-knd.html#SP23" class="internal">Kinds::new_base</a>
and <a href="4-nf.html#SP1" class="internal">NeptuneFiles::read_command</a> &mdash; there are two ways this can happen.
</li><li>&#9679; <span class="extract"><span class="extract-syntax">NOTIFY_NATURAL_LANGUAGE_KINDS_CALLBACK</span></span> is called when the kind "natural
language" is created (if it is): see <a href="2-fk.html#SP13" class="internal">FamiliarKinds::notice_new_kind</a>.
</li><li>&#9679; <span class="extract"><span class="extract-syntax">PROBLEM_KINDS_CALLBACK</span></span> is called when a syntax error is found, and can
prevent this from being issued to the terminal as an error message: see
<a href="1-km.html#SP5" class="internal">KindsModule::problem_handler</a>.
</li><li>&#9679; <span class="extract"><span class="extract-syntax">REGISTER_NOUN_KINDS_CALLBACK</span></span>, if provided, can register a common noun
for a new base kind with the lexicon itself. See <a href="2-knd.html#SP23" class="internal">Kinds::new_base</a>.
</li></ul>
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